Normally, an electrical junction box, also referred to as a junction block, a relay block, a branch joint box, etc., is formed by assembling a busbar substrate inside an upper and lower case. The busbar substrate comprises a series of busbars which are insulated from one another by an insulating substrate. Typically, the insulating substrate has insulating ribs for separating and providing insulation between the individual busbars. The insulating substrate has male tab openings through which the busbars' tabs extend in order to make connections between the respective busbars. The busbars also have tabs which project away from the insulating substrate and extend through male tab openings in the upper or lower casing to form male connectors. The male connectors in the upper and lower casing provide terminal ends for connection to the wiring harnesses in the motor vehicle.
FIG. 1 illustrates a conventional electrical junction box 101 having upper casing 102 and lower casing 103. Male connector 110 includes connector enclosure 104 formed on upper casing 102. Inside connector cavity 104 is a plurality of male tab openings 105. Housed between upper casing 102 and lower casing 103 is busbar substrate 106. Busbar substrate 106 comprises busbars 107 and insulating substrate 108. Busbars 107 form a prescribed circuit while insulating substrate 108 provides insulation between the busbars. At the ends of busbars 107 are tabs 109. Tabs 109 have sloping surfaces 109a (see FIG. 2) in order to facilitate mating.
Tab 109 passes through male tab opening 105 and into connector cavity 104 during assembly of junction box 101. Insulating rib 111 is formed on insulating substrate 108 to provide insulation between individual busbars 107. Tab openings 112 allow tabs 109 to pass through substrate 108.
In order to assemble junction box 101, the chuck (not shown) of an automatic assembling machine grasps busbar substrate 106 and mounts it inside lower casing 103. Then upper casing 102 is attached to lower casing 103, thereby completing the assembly of junction box 101. When upper casing 102 is attached to lower casing 103, tabs 109 pass through male tab openings 105 to form the male connector 110.
FIG. 2 shows a schematic cross section of the male connector 110 of a conventional junction box. Height L1 of insulating rib 111 is greater than height L2 of busbar 107. When condensation or the like forms within upper casing 102, short circuiting between the individual busbars 107 is prevented due to the fact that insulating rib 111 has height L1 which prevents droplets of water or dew from passing between the individual busbars 107.
Since height L1 of insulating rib 111 is greater than height L2 of busbar 107, there is a gap between busbar 107 and the bottom of upper casing 102 when tab 109 is passed through male tab opening 105. In order to stabilize tab 109 within male tab opening 105 and close this gap, enclosing rib 113 is formed around male tab opening 105. Enclosing rib 113 is formed integrally with the bottom of upper casing 102. Enclosing rib 113 presses down upon busbar 107 to securely hold busbar 107 in male tab opening 105. A bottom view of upper casing 102 is shown in FIG. 3a wherein male tab opening is encircled by enclosing rib 113.
It has been found that, during the assembly of the junction box, the alignment between male tab openings 105 and tabs 109 can be missed. This misalignment is depicted in FIG. 3b and can cause deformation in tab 109 resulting in busbar substrate 106 or upper casing 102 being damaged or destroyed. As will be appreciated by those skilled in the art, the assembly and description with respect to the misalignment that occurs with respect to upper casing 102, also occurs with respect to lower casing 103 in that in lower casing 103 also has male connector 110 along with enclosing rib 113.